The tear film and subjacent ocular surface will be studied in order to advance our understanding of the pathogenesis of drying of the ocular surface and in order to improve our ability to diagnose, assess and treat those disorders where ocular surface drying is clinically significant. The eyes of NZB/NZW F1 hybrid mice, a model for keratoconjunctivitis sicca (KCS), will be followed over time with morphological studies and tear osmolarity measurements as disease develops. The effect of infusing hypertonic solutions into the rabbit tear film wll be studied morphologically. A double-masked study will compare the therapeutic value of isotonic saline and a hypotonic saline solution. The effect of punctal occlusion on tear film osmolarity and rose Bengal staining will be studied. Corneal exposure will be examined in Graves' disease and Bell's palsy in order to ascertain the importance of the currently suspected coroneal exposure parameters, and in order to investigate the possible etiologic roles of elevated tear film osmolarity and dry spot formation in the pathogenesis of ocular surface disease.